Intravenous (IV) infusion sets are commonly employed to administer fluids containing medication and/or nutrients to both medical and surgical patients at a controlled rate. The rate may be controlled manually by adjusting a mechanical clamp on the IV tubing while counting drops falling through the drip chamber over a predetermined period of time to achieve a desired drop rate.
The amount of fluids to be administered to a patient is usually prescribed by the attending physician in cubic centimeters per hour, for example. It is necessary then for the operator to convert the drop rate into equivalent volumetric units. This is customarily done by dividing the drop rate by a number representing the so-called "drop factor" of the IV tubing. The drop factor varies with the size of the tubing and is expressed as a whole number, e.g., 10, 15, 20, 30, etc., marked on the package for the IV tubing, for example. Thus, in a particular case where the IV tubing has a drop factor of "10", for example, each volumetric unit, e.g. milliliter (ml), will produce 10 drops of liquid falling through the drip chamber.
While IV sets which are manually controlled in the aforesaid manner are quite simple and inexpensive to use, they are nonetheless time consuming and require experience and an ability to perform mathematical calculations in order to operate with any degree of accuracy.
Control devices for automatically regulating the flow rate of fluids in intravenous infusion sets have been developed such as those disclosed, for example, in U.S. Pat. Nos. 4,038,982 and 4,261,388. These devices generally include a valve for controlling the flow of fluid through the IV tubing and an electronic circuit for controlling the valve in order to establish a desired flow rate. A drop detector is usually also employed for sensing drops of liquid falling through the drip chamber.
Although control devices of this type are an improvement over prior manual techniques, they are nevertheless expensive and complex and generally require specially trained operators for their use. Moreover, most of these control devices are not capable of measuring the drop volume and also must be used with specific IV sets supplied with the device.
U.S. Pat. No. 4,173,224 to Marx et al. discloses an automatic IV regulator which employs an optical system for measuring the drop volume, but this system, while a distinct improvement, greatly increases the cost and complexity of the device.
It is therefore an important object of the present invention to provide a device for monitoring the volumetric flow rate of an infusion liquid flowing through an IV set which is inexpensive and which is easy to use.
Another object of the invention is to provide such a monitoring device which is portable and which can be used universally with any IV set employing tubing having any drop factor.
A more specific object of the invention is to provide a portable, self-contained, infusion monitor which can be easily attached to the drip chamber of one IV set and then quickly detached for use in another IV set without disturbing operation of either infusion system.
Another specific object is to provide such a portable, self-contained, infusion monitor which can be easily and quickly calibrated to accomodate IV sets employing tubing having varying drop factors.
Still another object is to provide such a portable, self-contained, infusion monitor which can visually display the volumetric flow rate of each drop of liquid falling through the drip chamber.